(1) Field of the Invention
This invention relates to production of ammonia mercerized cellulose. More specifically, this invention relates to treating cellulose fiber with vapors of ammonia to produce stable cellulose III polymorphs.
(2) Description of Prior Art
Heretofore, cotton cellulose in fiber, yarn and fabric was subjected to a conventional pretreatment with aqueous NaOH of "mercerization" strength (15-23%) to convert the cellulose I crystalline lattice to the cellulose II crystalline lattice which is more permeable to chemical solutions used in subsequent treatments. Although complexes of ammonia and cellulose were reported as early as 1936 Barry, A. J., Peterson, F. C., and King, A. J., "Interactions of Cellulose with Liquid NH.sub.3, J. Amer. Chem., Soc. 58, 333-337 (1936); and, Clark, G. L. and Parker, E. A., "X-Ray Diffraction Study of the Action of Liquid NH.sub.3 on Cellulose and Its Derivatives," J. Phys. Chem. 41, 777-786 (1937), the treatment of cotton cellulose with ammonia was only of academic interest until 1968 when a British patent, J. & P. Coates Ltd., et al British Pat. No. 1,136,417, Dec. 11, 1968 issued and described the use of liquid ammonia (NH.sub.3).
Interest by the textile industry in liquid NH.sub.3 pretreatments of cotton increased when Gogek, C. J., Olds, W. F., Volko, E. I., and Shanley, E. S. "Effect of Preswelling on Durable-Press Performance of Cotton," Textile Res. J. 39, 543-547 (1969) reported that liquid NH.sub.3 pretreatments improved wash-wear ratings and abrasion resistance of subsequently crosslinked cotton fabrics. However, all of the prior art teaches that the degree of conversion of cellulose I to a new crystalline lattice, cellulose III, depended upon the manner in which liquid NH.sub.3 was removed, Calamari, T. A., Jr., Schreiber, S. P., Cooper, A. S., and Reeves, W. A., "Liquid Ammonia Modification of Cellulose in Cotton and Polyester/Cotton Textiles," Textile Chem. and Color. 3, 61-65 (1971).
Even under optimum conditions, only partial conversion of I to III was obtained when NH.sub.3 was removed in the absence of water. In every case in the prior art, that part of the lattice partially converted to III reverted to Cellulose I or to decrystallized or amorphous cellulose when the product was immersed in water for subsequent chemical treatments as shown in Lewin, M. and Roldan, L. G., "The Effect of liquid Anhydrous Ammonia in the Structure and Morphology of Cotton Cellulose," J. Polym. Sci., 36, 213-229 (1971). All x-ray diffractograms published show only partial conversion to III even before contact with water and decrystallization to amorphous cellulose. Earlier work on the removal of NH.sub.3 at extremely low temperatures (-196.degree. C.) indicated a larger conversion to crystalline form III than when NH.sub.3 was removed at room temperature as seen in Jung, H. Z., Benerito, R. R.. Berni, R. J., and Mitcham, D., "Effect of Low Temperatures on Polymorphic Structure of Cotton Cellulose," J. Applied Poly. Sci. 21, 1981-1988 (1977). However, these partial conversions to crystalline form III readily converted to Cellulose I in the presence of water again showing serious instability.